The present invention relates to a method of casting a thin wall, that is a wall with a thickness of 0.050 of an inch or less.
Attempts to cast a thin wall with substantial extents along each of two axes have failed. However, it may be possible to use prior art methods to cast a thin wall having a very long dimension along a first axis and a very short dimension along a second axis. Thus, if a rectangular wall is to have a length of 32 inches and a width of 0.5 inches with a thickness of 0.050 inches, it may be possible to cast the thin wall with prior art methods.
When the width or minimum dimension of the thin wall is large compared to the thickness of the thin wall, the thin wall cannot be cast using prior art methods. It is believed that a thin wall having a thickness of less than 0.050 inches cannot be cast, using prior art methods, when the distance (L) from the center of the thin wall to a closest edge of the thin wall divided by the thickness (T) of the thin wall is equal to 40 or more.
In the foregoing example wherein the width of the rectangular thin wall was 0.5 inches, the distance (L) from the center of the thin wall to a closest edge would be one half of the width or 0.25 inches. When a distance of 0.25 inches is divided by a thickness of 0.050 inches, the result is 5, indicating that it may be possible to cast this thin wall with prior art methods.
If the width of the thin wall in the foregoing example is increased to four inches, the distance (L) from the center of the thin wall to the closest edge would be two inches. When a distance of two inches is divided by a thickness of 0.050 inches, the result is 40, indicating that this thin wall cannot be cast with prior art methods. The difficulty encountered in casting a relatively wide thin wall using prior art methods increases as the thickness of the thin wall decreases.
The reason that a relatively wide thin wall cannot be cast using prior art methods is that the gating necesary to conduct molten metal into the mold cavity will tear or badly distort the thin wall as the mass of molten metal in the gating solidifies and cools. Therefore, thin walls having (1) a thickness of 0.050 of an inch or less, (2) a surface area of at least sixteen square inches, and (3) a minimum dimension across the surface of at least four inches have not been cast using prior art methods. The problem of making a thin wall having substantial extents in all directions from the center of a surface of the thin wall has previously been solved by casting a thick wall and then machining the wall to reduce its thickness.